In various mechanical devices, and particularly within a transmission of an automotive powertrain, specialized overrunning clutches or one-way clutches are used to produce a one-way driving connection between input and output members of the transmission. A one-way clutch typically has a pair of plates or races, and is capable of selectively transmitting torque between the races when the rotation of one race with respect to the other is in one direction, with the clutch “overrunning” or freewheeling when the rotational direction is reversed.
The relative shape and/or orientation of the races may vary depending on the particular design of the one-way clutch. The mechanical means used to lock a typical one-way clutch are varied, but commonly consist of torque-transfer elements such as diodes, rollers, sprags, rockers, prawls, or struts that are positioned between the races. Depending on the particular type or style of one-way clutch and the direction of rotation, each race may include unique features such as wells or notches suitable for engaging one or more of the torque-transfer elements in order to selectively enable various clutch operating states or modes.
In a basic one-way clutch, the operating mode is determined by the direction of the torque being applied to an input race of the clutch. A selectable one-way clutch or a SOWC potentially provides additional utility relative to the conventional one-way clutch, with a SOWC being capable of producing a driving connection between the input and output races in one or both rotational directions. A SOWC can also freewheel in one or both rotational directions as needed. One of the two races of a conventional SOWC can be indexed or grounded to a stationary member, such as a transmission case or center support. However, the grounding of one race prevents such a SOWC from being used in applications where both races are allowed to rotate.